Circuit breaker



Oct. 13, 1959 Filed April 4, 1957 G. W. KIESEL ETAL CIRCUIT 'BREAKER 5Sheets-Sheet l INVENTORS -4 GEORGE W Klssu.

EMERY M. WEGH ATTOPNE Y s. w. KIESEL ETAL 2,908,782

CIRCUIT BREAKER Filed April 4, 1957 5 Sheets-Sheet 2 INVENTORS GEORGE W.KIESEL, EMERY M. \A/EGH WM? C ATTORNEY Oct. 13, 1959 w. K!ESEL ETAL2,908,782 szacuzw BREAKER Filed April 4,, 195'? 5 Sheets-Sheet 5 GzoaesW. KasszL, EMERY M. Wren WM/9? G ATTORNEY Oct. 255 G. w. KIESEL ETAL2,908,782

CIRCUI'IY BREAKER Filed {it 5 Sheets-Sheet INSULATION INSULATIONINVENTORS' GEORGE W. KlzscL, EMERY M.\/\/EGH ATTORNEY INSULATION UnitedStates Patent CIRCUIT BREAKER George W. Kiesel, Bristol, and Emery M.Wegh, Terryville, Conn., assignors to General Electric Company, acorporation of New York Application April 4, 1957, Serial No. 650,599

12 Claims. (Cl. 200-88) Our invention relates to electric circuitbreakers and particularly to multipole electric circuit breakers of thetype including a molded insulating casing and adapted for use, eithersingly or in panelboards, for the control of electric light and powercircuits in residential, commercial and industrial buildings.

In recent years, relatively small, compact, plug-in type single-polecircuit breakers have become popular for use in residential, commercial,and industrial buildings. A circuit breaker of the type referred to isshown, for instance, in Patent No. 2,627,563, issued February 3, 1953,to W. A. Thomas and assigned to the same assignee as the presentinvention. Panelboards of the type containing contacts adapted toreceive such plug-in circuit breakers, also in wide use, are shown inPatents No. 2,738,445, and 2,738,446, issued March 13, 1956, to H. J.Hammerly et al. and to W. J. Fleming, respectively, and also assigned tothe same assignee as the present invention.

Such compact plug-in circuit breakers have heretofore been availableonly in single-pole and two-pole forms, rated to 50 amperes at 125volts. There has for some time been a need, however, for three-polecircuit breakers of this type and size, which can also be plug-inmounted in such panelboards. Such three-pole circuit breakers haveheretofore not been available because of the difficulty of providing onewhich will meet the electrical requirements in the small spaceavailable. Such a breaker must, for instance, be rated at substantiallydouble the voltage of the single and two-pole devices, i.e., 240 volts,and at currents of the same or greater value, i.e., 10-70 amperes, whileoccupying substantially the same space per pole as the single poleversion.

The problem is further illustrated by comparing the size of the requiredthree-pole plug-in breaker with that of the smallest three-pole breakerof similar rating in general use heretofore. Such a prior three-polecircuit breaker, generally as shown in Patent No. 2,640,127 issued May26, 1953, to R. N. Rowe and assigned to the same assignee as the presentinvention, has the following dimensions: 4 /8" x 6" x 3%" or a volume of83.5 cubic inches. The three-pole breaker required by the plug-inpanelboards referred to above, and which is provided by applicantspresent invention, has the following dimensions: 3 x 3%" x 2 /8 or avolume of 27 cubic inches. It will be seen that the prior breaker isapproximately three times the size of the breaker of the presentinvention.

It is, therefore, a general object of our invention to provide anextremely compact and efiicient multipole circuit breaker and especiallya compact and efficient plug-in type multiple circuit breaker, suitablefor use in existing plug-in type panelboards.

In providing such a compact multipole circuit breaker, it is necessaryto provide (1) an operating mechanism capable of supplying a sufiicientamount of contact pressure to each of three sets of contacts, (2) areextinguish- 2,908,782 Patented Oct. 13, 1959 ICC? ing means or arechutes large enough to contain and extinguish relatively high voltagearcs, and (3) thermal and magnetic tripping mechanism for each pole,capable of operating quickly and of withstanding momentary high shortcircuit currents. These primary circuit breaker components must beadequate to perform their particular functions and must also be of asize able to be contained in the small space available. In addition, aninsulating housing must be provided, and these components must be soarranged and spaced with respect to each other within the housing thatflash-over does not occur from one part to another on high voltagesurges, even after severe arcing, and provision must also be madewhereby the critical operating parts are shielded so as not to beburned, distorted or destroyed by the heat of such high power areinterruptions.

Such flash-over may occur during or following an opening operation ofthe circuit breaker, between the stationary contact, which is at onepotential after opening and some other metallic part such as the movablecontact, the operating mechanism, or the trip device, all of which areat a potential opposite to that of the stationary contact after opening.Breakdown or flash-over may also occur from pole to pole within thebreaker when the breaker is in closed condition.

It is an object of our invention to provide a compact multiple circuitbreaker having its operating mechanism isolated from its arcinterruption chamber.

It is another object of our invention to provide a compact multiplecircuit breaker having the tripping mechanism for each pole isolatedfrom other tripping mechanisms and from the arc interruption chamber andalso effectively shielded from the efiects of arc chamber exhaust gases.

It is a further object of our invention to provide a circuit breakerhaving a pro-assembled operating mechanism which can be easily, quickly,and accurately mounted within a recess in an insulating casing.

It is a further object of our invention to provide a circuit breakerincluding a multi-part insulating casing adapted to receive and supportthe circuit breaker parts, in which different, selected, materials areused in such a way as to provide dimensional stability where criticallyneeded to support and space the mechanism parts, and to provide arcresistance where needed to guard against arcing or flash-overrespectively.

Other specific objects will in part be pointed out and in part becomeapparent as the following detailed description proceeds.

In accordance with our invention, we provide a compact multipole circuitbreaker having an insulating casing with a number of side-by-side polechambers, each containing a stationary contact within an arcextinguishing chamber or chute. An operating mechanism of the overcenterspring type is located in one of the pole chambers above the arc chutesand simultaneously operates a plurality of contact arms each pivotedabove the respective one of the arc chutes and adapted to move throughthe chute to engage the stationary contact thereon. A bimetal tripdevice has a portion extending alongside each arc chamber forindependently or conjointly tripping the mechanism; and means areprovided for effectively shielding the casing, the operating mechanism,and the trip devices from carbonizing, burning, welding, heat distortionor other adverse effects often caused by are interruption products,especially during interruption of short circuit currents. Such shieldingis, in accordance with our invention, provided by a novel arrangementand configuration of the circuit breaker parts themselves as well as bythe provision of protective insulating material at strategic locations.By this means, although no particfiular venting provision is made in theinsulating casing, the explosive products of arc interruption undershort circuit current conditions are either contained within the arcinterruption chamber, or, even though extending into other parts of thecircuit breaker housing, are prevented from coming directly in contactwith critical portions of the circuit breaker and tripping mechanism.

In accordance with one aspect of our invention, we provide a compactmultipole circuit breaker having a generally rectangular insulatingcasing which is made up of two housing members, one member containing apreassembled operating mechanism and supporting the trip devices withrespect thereto, and the other member mounting only the stationarycontacts and are chutes and providing room for a portion of the tripdevices.

In accordance with another aspect of our invention,

the two housing members comprise different materials respectively, onemember being molded of a material of high dimensional stability toassure accurate spacing of the operating mechanism relative to the tripdevices, and the other member being molded of a material of high areresistance material to minimize adverse effects of arc interruption.

, In accordance with a further aspect of our invention, the operatingmechanism is pre-assembled in its own supporting frame and is merelyinserted into the corresponding recess in the top portion of thehousing. It is accurately positioned by projections carried by the outersides of the frame and received in tapering grooves in the casing walls.The assembled mechanism is retained in the recess, when the top andbottom are assembled, by retaining means carried by the bottom partacting on compressible portions of the side frames.

Whilethe specification concludes with claims particularly pointing outand distinctly claiming the subject matter whichwe regard as ourinvention, it is believed the invention will be better understood fromthe following detailed description taken in connection with theaccompanying drawings in which:

Figure 1 is a side elevation view of a three-pole circuit breakerconstructed in accordance with our invention, the side of the enclosinghousing being removed to show the parts, and the circuit breaker beingshown in the normal open-circuit condition;

Figure 2 is a side elevation view similar to Figure 1 but with thecircuit breaker shown in the closed-circuit condition;

Figure 3 is a sideelevation view similar to Figure 1 but with thecircuit breaker shown in the automatically opned or tripped condition;

Figure 4 is an exploded view of the insulating housing of the circuitbreaker of Figure 1, shown as in Figures 1-3;

Figure 5 is a perspective view of the operating mechanism and movablecontact assemblage of the circuit breaker of Figure 1, parts thereofbeing broken away;

Figure 6 is an exploded view of the parts of the circuit breaker ofFigure 1, including the operating mechanism, movable contact assemblage,and one line terminal, arc chute, trip device and load terminal;

Figure 7 is an end elevation view of the circuit breaker of Figure l asviewed from the line terminal end;

Figure 8 is an end elevation view of the circuit breaker of Figure l asviewed from the load terminal end, a portion of one of the load terminalclamping members being broken away;

Figure 9 is an exploded view of the circuit breaker of Figure l asviewed from the side thereof;

Figure 10 is a view of the top housing member, taken on the line 1l10 ofFigure 9, the operating mechanism and trip devices being omitted;

Figure 11 is a view of the bottom housing member taken on the line 1111of Figure 9, one of the arc extinguishing structures being omitted andtwo are extinguishing chamber covers being omitted; and

Figure 12 is a detail view showing a modified form of common trip barfor use in the circuit breaker of Figure 1; and

Figure 13 is a sectional view of a modified form of the invention, shownas incorporated in a two-pole circuit breaker.

In the drawings, we have shown our invention as embodied in a three-poleelectric circuit breaker having a generally rectangular insulatinghousing comprising a top housing member 10 and a bottom housing member11 adapted to be connected together by suitable means such as by tubularrivets 12, Figure 9, passing through holes 14, Figures 10 and 11, in thetop and bottom housing members respectively. Referring to Figures 10 and11, the top housing member 10 has three elongated recesses 15, 16 and 17extending substantially from end to end thereof and separated bybarriers 18 and 19 integral with the top housing member. The bottomhousing member 11 is also provided with three elongated generallyparallel recesses 26, 21 and 22 therein separated by barriers 23 and 24also integral with the bottom housing member.

The barriers 18 and 19 are cut away at 18' and 19' to provide anunobstructed transverse passageway at the front of the top housingmember 19 for a purpose to be described. The barriers 23 and 24 are cutaway at 23 and 24' to provide an unobstructed transverse passageway atthe back portion of the bottom housing member 11 for a purpose to bedescribed. The recesses 15, 16, 17 are adapted to register with therecesses 20, 21, 22 when the top and bottom housing members 10' and 11are assembled together to provide three elongated closed recesses orpole chambers.

Each of the recesses 20, 21 and 22 has supported within it at one endthereof a plug-in type line contact socket 25. The socket 25 comprises agenerally U-shaped member, Figure 6, having the legs thereof broughtcloser together at their extremities than at the bight of said U, and agenerally U-shaped resilient reinforcing clip member- 26 embracing thesides of said U-shaped line contact member adjacent their extremities.The bottom housing member 11 is provided with three L.-shaped cornerslots 27 providing access to said line contact socket 25 by suitablemeans such as by a blade-type contact (not shown).

The line socket 25 further includes a contact supporting portion 28integral therewith and extending from the bight of said U and having astationary contact 29 fixedly attached thereto by suitable means such asby welding.

For the purpose of cooling and extinguishing arcs adjacent saidstationary contact 29, we provide arc extinguishing means adjacent eachof the stationary contacts 29 and including a generally U-shapedinsulating support 30, Figures 6 and. 11. The U-shaped insulating member30' is preferably formed of a strong sheet insulating material such asvulcanizing cellulosic fiber, and supports between the sides thereof aplurality of notched metallic arc extinguishing plates 31. The U-shapedinsulating piece 30 is supported in place by the corresponding outerwalls of the bottom insulating housing member 11, by portions of thebarriers 23 and 24, and also by short transversely extending barriers 32integral with the outer walls and the barriers of the bottom housingmember 11. The transversely extending barriers 32 are cut away ornotched to provide an entrance portion 33 to each of the arcextinguishing chambers.

Barriers 131 serve. to provide isolation of the upper portions of thetrip devices in the two outer poles from the arc chambers and also serveas stops to limit whipping or resilient overtravel of the, contact armsin these poles.

The stationary contact supporting portion of the line contact 25 extendsover the top edge of the bight wall of the U-shaped' member 30, therebysupporting the line contact member 25 in place in the recess 20. Theline contacts-25 are further supported in their respective chambers byshoulders 34 integral with the bottom insulating housing member 11 whichare adapted to engage corresponding shoulders 35 on the line contactmember. The contact support 28 is shielded from the effects of arcing bya generally U-shaped fiber insulating piece 30'.

Three movable contacts 36 are provided, each being rigidly attached tothe outer end of resilient contact arms 37 which in turn are rigidlyattached to an insulating contact cross arm 38. The contact supportingarms 37 are preferably shielded by insulation strips 39 as shown,especially in high amperage rating devices.

The insulating contact cross arm is supported for movement by agenerally U-shaped contact operating member 40. The contact operatingmember 40 is provided with two aligned slots 41 adjacent the bightthereof, and the contact cross arm 38 extends through the aligned slots41 and is rigidly attached to the bight of the contact operator 40 bysuitable means such as by rivets 42. It will be observed however thatthe contact cross arm 38 is supported on the operating member 40 atthree points, i.e., against the bight portion of the contact operator 40and against the edges of the slots 41 formed in the side portions of thecontact operator 40. This supporting arrangement not only distributesthe stress exerted on the contact cross arm 38 by the contact operator40, but also restrains any tendency of the contact cross arm 38 towardwarping or twisting. The contact operating member 40 is supported in thetop housing member for rotation about a fixed pivot 43 and is adapted tobe operated between open and closed circuit positions in a manner and bymeans'to be described.

The circuit breaker of our invention also includes three load connectingterminals each comprising a load terminal strap 44 which is generallyL-shaped and has its outer extremity bent downwardly to retain thereon agenerally tubular wire clamping member 45 which may be of steel, andwhich carries a wire clamping screw 46. The load terminal strap 44 hasits inner portion extending within each of the recesses 15, 16 and 17 ofthe top housing member 10 respectively and is anchored to the tophousing member by a clamping screw 47 extending through a slot 48 in theend wall of the top housing member 10 (see particularly Figures 8 and10) and into threaded engagement with the vertical portion of the loadterminal strap 44. The extreme inner end 49 is returnbent, and hasfixedly attached thereto an elongated bimetallic strip 50. For thepurpose of adjusting the normal position of the bimetallic strip 50 withrespect to the insulating housing member 10, we provide a calibratingscrew 51 threadedly engaging the vertical portion of the terminal strap44 and adapted to exert a pressure against the upper portion of thebimetallic strip 50.

For the purpose of preventing current flow between screw 51 and thebimetallic'strip 50, an insulating member 52 is provided which isgenerally T-shaped and adapted to extend through an opening 49 in thebight portion of the return-bent portion 49 of the terminal strap 44.The lower end of the bimetallic strip 50 is connected by a flexibleelectrical conductor 53 to the movable contact 36. In order to protectthe flexible conductor 53 from the effects of arcing, we provide an insulating sheath of woven glass fiber material 54.

The flexible braid 53 is attached to the contact supporting arm 37directly behind the movable contact 36. It will be observed, especiallyby reference to Figure 1, compared to Figure 2, that the flexible braidundergoes a severe sharp bending immediately adjacent the movablecontact 36. This bending is so sharp that, with ordinary methods ofattachment, breakage would occur in the flexible conductor at this pointafter a number of operations of the breaker. Such breakage is preventedin the present design however by means of a supplementary supportingclip 55. The clip 55 includes a generally U-shaped portion, the outerends of the U being bent over the edges of the contact supporting arm37, and the intermediate portion of the U encircling the flexibleconnector immediately adjacent the point at which it is welded to themovable contact. The clip 55 further includes an arcuate tang portionextending from the bight of the U and adapted to engage the flexibleconnector and to prevent the connector from bending too sharply at thispoint of connection (see particularly Figure 1 and Figure 3).

The current path may now be traced through the circuit breaker in thefollowing sequence: Current enters at the line contact 25 and goes tothe stationary contact 29, to the movable contact 36, through the endportion of the contact supporting arm 37 to the flexible conductor 53,to the bimetallic strip 50, to the load terminal strap 44.

For the purpose of moving the contact operator 40 about its pivot 43 tomove the movable contacts between open and closed circuit positions, andto releasably retain such contacts in the closed circuit position, weprovide a circuit breaker operating mechanism 56 shown in perspective inFigure 5 and shown in exploded relation in Figure 6. The operatingmechanism shown is disclosed and claimed in application Serial Number650,600, filed April 4, 1957, by Emery M. Wegh and assigned to the sameassignee as the present application.

The operating mechanism includes two opposite side frame members 57 and58, supported in spaced-apart relation by spacer pins 59 and 60. Thespacer pins 59 and 60 include shouldered portions for supporting andspacing apart the side frame members and also integral extensions 61 and62 adapted to project through the side frame members and to extendoutwardly from the outer side of such frame members for a purpose to bedescribed.

A releasable carrier member or trip member 63 is supported for pivotalmovement between the side frames 57 and 58 on a carrier pivot pin 64.The carrier pivot pin 64 is also shouldered and aids in spacing the sideframes 57 and 58. Upper and lower pairs of toggle links 65 and 66respectively are also provided. The upper pair of toggle links 65 extendone on each side of the carrier 63 and are pivotally supported thereonat one end by a pivot pin 67. The lower pair of toggle links 66 are morewidely spaced apart and are individually pivoted on the U-shaped contactoperator 40 by short pivot pins 68. The upper and lower pairs of togglelinks 65 and 66 have their mutually adjacent ends connected andsupported by a toggle knee pin 69. The upper toggle links 65 arepivotally supported on a central enlarged portion of the pivot pin 69,and the more widely spaced lower toggle links 66 are pivotally supportedon reduced outer portions of the pivot pin 69. The pivot pin 69 isterminated at the outer surface of the lower toggle links 66 and isheaded over to retain the links 66 thereon.

A pair of tension-type operating springs 70 are supported at one end ingrooves in a relatively stationary spring anchor pin 71 which extendsfrom side to side of the mechanism and has reduced end portions 72resting in notches 73 cut in the corners of a projecting portion of themanually operating member 74. The lower ends of the operating springs 79are attached to the toggle knee pivot pin 69, on the portion of the pinbetween each of the adjacent ends of the upper and lower toggle links.The manual operating member 74 is pivotally supported on knife-edge typepivots by means of notches 75 therein adapted to rest on outwardly bentlug portions 76 integral with the side frame members 57 and 58respectively. The manual operating member 74 is provided with a manuallyengageable insulating handle portion 77 having a portion adapted toproject through an aperture 78 in the top wall of the top housing member10 and having an arcuate enlarged portion within the casing housingadapted to close the remaining portron of the aperture 78 in allpositions of the handle.

The insulating handle member 77 is adapted to be carried by theoperating member 74 and to operate the member 74 by means ofinterfitting portions'including shoulders 79 on the insulating handle 77and edge portions 80 of the operating member 74. For the purpose offacilitating assembly of the operating mechanism and the insulatinghandle 77 into the top housing member in a manner to be described, atemporary holding clip 81, Figure 6, is provided, comprising a generallyU-shaped length of resilient wire having portions bent over so that itsside portions are L-shaped, and hooked in under the top bight portion ofthe handle member 74. The handle member 74 has a portion of the bightthereof lanced out and offset from the general plane thereof therebyproviding an opening to receive the clip 81 and also a support toprevent the clip 81 from falling within the operating member 74.

Assuming the carrier member 63 to be stationary in the position shown inFigures 1 and 2, the switching action of the operating mechanism may bedescribed as follows. In Figure l the parts are shown with ,the movablecontact in the open circuit position and the toggle links 65 and 66 inthe collapsed condition. As the handle member 77 is moved forward torotate the operating member 74- in a clockwise direction, the upper endsof the operating springs 70, carried by the spring anchor pin 71 arecarried in a clockwise direction until the line of action of the springs70' passes across the pivot pin 67 of the upper toggle links 65. Whenthis occurs, the springs 70 exert a force on the toggle knee pin .69urging it to the right as viewed in Figures 1 and 2, toward a togglestraightened position. The parts then quickly move to the position shownin Figure 2, with a snap action. In this position, the resilient contactarms 37 are slightly deformed, exerting a predetermined contact pressurebetween the movable contact 36 and the. stationary contact 29.Conversely, when the handle member 77 is moved to the left as viewed inFigures 1 and 2, the upper ends of the operating springs 70 are carriedin a counterclockwise direction and when the line of action of thespring 78 passes across the pivot pin 67, the toggle links move to acollapsed position with a snap action and the parts return to the normaloff position shown in Figure 1.

For the purpose of releasably restraining the carrier member 63 in thenormal or latched position shown in Figures 1 and 2, we provide aretaining latch 83, pivoted between the side frame members 57 and 58 at84, and having an aperture 85 adapted to receive a latching portion 86of the carrier 63.

For permitting operation of the latch member 83 by any one of two ormore trip devices in a manner to be described, we provide an insulatingcommon-trip bar 87 which extends transversely across all three polecompartments 20, '21 and 22 of the bottom housing member 11. Thecommon-tripbar 87 is preferably formed of a highly arc-resistant andheat-resistant material so as to withstand the efifects of arcing fromthe arc chambers and to shield the current responsive trip assembly (tobe described). Suitable materials for the trip bar 87 includeglass-bonded mica or Mycalex, polyester and epoxy molding compoundsreinforced by glass fiber, plastic resin bonded asbestos, and ceramicmaterials such as porcelain and bonded alumina. The commontrip bar 87 isrigidly attached to the retaining latch 83 by suitable means such as byrivets 88, and has a central portion 89 provided with a hole 90 adaptedto receive one end of a trip bar biasing spring 91, the other end ofwhich is anchored on the frame spacer pin 59. The action of the trip barbiasing spring 91 is such as to constantly bias the common-trip bar andthe latch member 83 in a clockwise direction into latching engagementwith the latch portion 86 of the releasable carrier 63.

It will be observed that in the normal oil? and on conditionsshownin'Figures 1 and 2 respectively, the operating springs are undertension, placing the upper toggle links 65 in compression and exerting aforce on the releasable carrier 63 through the pin '67, which tends tomove the releasable carrier 63 in a clockwise direction as viewed inFigures 1 and 2. Such movement of the carrier 63 is normally restrainedby the latching engage ment of the projection 86 with the retaininglatch 83.

For the purpose of providing both thermal and mag= netic currentresponsive tripping action, we provide each pole of the circuit breakerwith a bimetallic strip 50 described above, adapted to carry currenttherethrough, and, in addition, a magnetic armature member 110. Thearmature 110, shown more clearly in exploded view Figure 6 includes abifurcated main portion terminating in upper bearing surfaces 111 eachadapted to pivot in knifeedge fashion in molded bearings 112 (see Figure4) in the top housing member 10. The armature is retained in mountedengagement in the V-shaped pivot bearings 112' by means of an armaturebiasing spring 113, which has one end hooked into a lanced-out portion114 of the load terminal strap 44, and has the other end connected by aninsulating link 115 to a projecting tongue 110' integral with the lowerportion of the armature 110. The magnetic armature 110 is furtherprovided with an integral flag-shaped portion or extension 116 havingits outermost portion bent downwardly so as to present an edge 117 whichis adapted to extend in front of the lower extremity of the bimetallicstrip 50. The armature biasing spring 113 biases the armature 110: in aclockwise direction and normally maintains the edge 117 against theforward surface of the bimetallic strip 50.

A magnetic core member 118 is also provided, being attached to the lowerportion of the bimetallic strip 50 by suitable means such as by welding,and is generally U-shaped to present pole portions 118 at either side ofthe bimetallic strip 50*.

The operation of the thermal and magnetic trip device is as follows.Assuming the breaker to be in the closed circuit condition of Figure 2,during a continued overload condition which is below a short circuitvalue, the bimetallic member 50 is heated by the action of currentpassing therethrough, and deflects or warps in a way to cause the lowerend thereof to move to the right as viewed in Figures 1 and 2. As thelower end of the bimetallic strip 50 moves to the right, it exerts forceagainst theedge 117 of the armature 110 and carries the armature 110with it, until the toe portion of the armature extension 116 engages thecommon trip bar 87. Continued movement of the bimetal 50 and thearmature 110 to the right moves the lower end of the trip bar 87 to theright, rotating the latch member 83 in a counterclockwise direction andwithdrawing the retaining edge of the aperture 85 from the latch portion86 of the carrier 63. Upon release of the latch portion 86, theoperating springs 70 move the carrier member 63 in a clockwise directionuntil the extension 119 on the carrier 63 strikes the spacer pin 60.

As this rotation of the carrier member 63 occurs, the pivot pin 67 ofthe upper toggle links is carried across the line of action of theoperating springs 70, thereby reversing the rotational bias of theoperating springs 70 i on the upper toggle links, collapsing the togglelinks and moving the movable contacts to the open circuit position asshown in Figure 3. The movement of the movable contact operator andcontact arms toward the open circuit position is limited by the contactoperator 40 striking the pivot pin 64 of the carrier member 63. Thistripping action occurs regardless of whether the movable operatinghandle 77 is forcibly restrained in the on position such as by anoperators hand. When the operating handle 77 is released, however, thehandle member 77 is automatically returned to a central position asindicated in Figure 3 by further action of the operating spring 70. Thishandle-return action takes place because the lower endsof the operatingsprings 70 have been moved to the left by the collapsing action of thetoggle links, and therefore the line of action of the operating springs70 now passes to the left hand side of the handle pivot point 75 asviewed. This return movement of the manual operating member 77counterclockwise as described, is

limited by the engagement of a resetting pin 120 carried by andextending from side-to-side of the manual operating member 74, which pinengages a resetting cam portion of the edge of releasable member 63.

In order to reset the circuit breaker, assuming that the bimetallicmember 50 has cooled sufficiently to permit the latch biasing spring 91to return the latch member 83 to proper position, the manuallyengageable handle portion 77 is moved manually from the central positionor trip position of Figures 3 to the normal oif or resetting position ofFigure 1. During this movement, the resetting pin 120 rides'along theresetting cam portion 121 of the carrier 63 and rotates the carrier 63counterclockwise about its pivot 64 until the latching projection 86once again enters the aperture 85 in the latch 83. At this point, thelatch biasing spring 91 returns the latch 83 to its extreme clockwiseposition, such clockwise movement being limited by the engagement of theportion of the latch 83 immediately below the aperture 85 with the edgeportion of the carrier member 63 immediately below the latchingprojection 86, assuring a fixed, predetermined maximum latch engagement.

Instantaneous or magnetic tripping action occurs when currents of ashort circuit magnitude pass through the circuit breaker and through thebimetallic strip 50. When this occurs, the magnetic field associatedwith such current forms magnetic poles at 118' of the core member 118,thereby creating an attraction between the armature 110 and the magnet118. Since the bimetallic strip 50 is relatively stiff compared to theresilience of the magnetic armature biasing spring 113, the armature 110moves to- Ward the bimetallic strip 50 and toward the magnet 118 asshown in Figure 3. When this occurs, the toe portion of the armatureextension 116 engages the common trip bar 87 and rotates the latchmember 83 in counterclockwise direction, causing tripping in the samemanner as described above. Resetting following such magnetic tripping isaccomplished in the same manner as previously described in connectionwith thermal tripping.

As mentioned above, the exact calibration of the circuit breaker may bealtered by adjusting the calibrating screw 51 which exerts a forcebetween the main portion of the terminal strap 44 and return bentportion 49 which carries the bimetallic strip, either opening it outwider or allowing it to return to a more nearly closed position byreason of its resilience. This adjusts the angular position of thebimetallic strip 50 with respect to the remaining parts of the circuitbreaker and particularly with respect to the common trip bar 87.

In Figure 13 we have shown our invention as embodied in a two-polecircuit breaker. The construction in this form is substantiallyidentical to that of Figure 1 excepting that the casing includes onlytwo pole chambers, and the contact cross-arm 38 and the common trip bar87 have been shortened correspondingly.

In Figure 12 we have shown a modified form of common trip bar. In thismodification, the common trip bar 122 instead of being formed entirelyof insulating material, is formed of a metallic material such forinstance as aluminum, which is coated with a suitable coating 122 ofinsulating material, such for instance as an epoxy resin plastic. Wehave found that an aluminum common trip bar treated so as to have analuminum oxide coating thereon and subsequently given a coating ofinsulating plastic particularly nylon performs satisfactorily.

In order to support the operating mechanism of our improved circuitbreaker in such a manner as to pro- 10 tect it from the effects of arcinterruption in the closely adjacent arc-interrupting chamber, We havedevised an arrangement and supporting means whereby the completelyassembled mechanism is inserted and supported in the upper half of theinsulating housing, that is, in housing member 10, and We have likewisedevised means whereby the trip devices for each of the three poles ofthe circuit breaker is also supported in the upper half of theinsulating casing, that is in housing member 10, and particularly issupported in such housing member with respect to the operating mechanismand its associated latch and trip bar. Accordingly the operatingmechanism is provided with relatively short projections 61 and 62described above extending outwardly from the outer surfaces of the sideframe portions 57 and 58.

In addition, the central chamber 16 of the upper housing member 10 isprovided with two pairs of recesses or slots 123 and 124 adapted toreceive the projections 61 and 62, respectively. The slots 123 and 124are also provided with an intermediate portion which is slightlyconstricted so as to aiford a defeatable resistance to the entry of theprojections. In addition, each of the side frame members 57 and 58 isprovided with an integral vertically deformable portions 125 for apurpose to be described.

The distance between the side frames 57 and 58 is preferably made lessthan the corresponding distance between the barriers 23 and 24 of thelower housing member 11, so that in the two pole form the width of thecircuit breaker may be reduced to eifectively two thirds that of thethree pole form without interfering with the mounting and support of theoperating mechanism thus permitting the same mechanism to be used forboth the two and three pole forms. For the purpose of supporting themechanism in the upper housing member 10 and in the downwardly openingslots 123 and 124, as well as for the purpose of further isolating theoperating mechanism from the arcing products produced in the lowerchambers, we provide arc extinguishing chamber covers 126. Each of thearc extinguishing chamber covers 126 is supported on ledges 127 in eachof the recesses 20, 21 and 22, and has a slot cut therein to permit theentry of the contact operating arms 37 in the outer pole chambers 20 and22, the arc extinguishing covers 126 serve primarily to isolate theeffects of arcing in each of the associated chambers. In the centralchamber 21, the arc extinguishing cover 126 performs this same functionand in addition provides a supporting base which is adapted to engagethe deformable portions 126 of the side frame members 57 and 58 and tothereby hold the operating mechanism in its proper location in the upperhousing member 10.

The two deformable portions 125 are initially formed so as to extendbelow their finally assembled position. So that as the housing membersare placed together and suflicient force is exerted the portions 125 aredeformed slightly, thereby providing a resilient retaining force toretain the mechanism in position.

The assembly of the complete three pole circuit breaker thereforepreferably follows the following sequence. First the operating mechanismis assembled between the side frames 57 and 58 with the movable contactarms and movable contacts, and also with the flexible conductors 53 andeach of the bimetallic strips 50 and load terminal straps 44 andconnectors 45 attached thereto. The handle member 77 is inserted inplace on the manual operating member 74 being resiliently retainedthereon by the retaining clip 81. The top housing member 10 may then beinverted and the assembled mechanism inserted therein so that theprojections 61 and 62 rest in the entrance portion of the slots 123 and124. Additional manual pressure upon the side frames 57 and 58 causesthe projections 61 and 62 to snap into their final location in theextreme portion of the slots 123 and 124. This subassembly may thereforebe conveniently handled before the addition of the lower housing member11 without the mechanism falling out. The trip devices including thebimetallic strips and load terminal straps are then inserted intocorresponding recesses in the top housing member the load terminal strapmounting screw 47 being already inserted in its threaded hole therein,such assembly being permitted by the entrance slot 48. The load terminalstrap mounting screw 47 is then tightened mounting the load terminalmember and bimetal in fixed position in the upper housing member.Following this, the armature members 110 are assembled by hooking theextension portions 116 around the extreme end of the bimetallic strip 50and placing the bearing edges 111 in the corresponding molded bearings112 in the casing, and by hooking the armature biasing spring inposition between the terminal strap and the armature. It will beobserved that the armature biasing spring 113 serves not only to biasthe armature member 110 into mounted condition in its inverted V-shapedbearings in the upper housing member, but also to bias it clockwise sothat the edge 117 is normally maintained in proper engagement with thesurface of the bimetallic strip St). Following assembly of the parts inthe upper housing member 10, the arc extinguishing assemblies comprisingthe support member 30 the arc plates 31 and the line contact member 25carrying the stationary contact 29 are assembled as one unit into thecorresponding recesses in the lower housing member 11. The areextinguishing cover members 126 are then placed over the arcextinguishing assemblies. The circuit breaker is then ready for thefinal assembly operation and is in the condition shown in Figure 9. Thetop and bottom housing members are then brought together and suflicientforce exerted to deform the deformable portions 125 of the side frames57 and 58 and rivets 12 are passed through the aligned holes 14 in thetop and bottom housing members and spun over to retain the partstogether. It will be observed that following such final assembly, theclamping member 45 encircling the load terminal strap 44 and the tubularclamping member 45 are supported by an insulating piece 130 which inturn is sup ported by projecting bosses 128 projecting from extensionsof the side wall portions and of the barrier portions 23, 24 of thebottom housing member 11. In the form shown in Figure 8, the strap 44and the member 45 are supported directly by the bosses 128 and the piece130 is omitted.

The completed circuit breaker is adapted to be held in mounted conditionby suitable retaining means (not shown) adapted to engage projectingledges 129 below the load terminal members 45. The design of the ledgesmembers 129 and the bosses 128 is such as to remove the necessity forundercutting in the molding of the bottom housing member 11. Accordinglythe design is such that no part of the lower housing member 11 projectsdirectly above the ledge surface 12?, the bosses 128 being offset to oneside of such vertical location. It will be observed that the design ofthe housing is such that top and bottom mating housing members 10 and 11are provided each including three registering longitudinal recesses 15,16, 17 and 2t), 21, 22 separated by registering barriers 18, 19 and 23,24, and that these recesses each of which serves as a separate polechamber, are crossed by a transverse passageway, the transversepassageway being offset longitudinally and located at op posite ends ofthe circuit breaker proper. In this manner maximum isolation and maximumcompactness is achieved.

We furthermore provide a circuit breaker which meets all the requiredtests referred to above at a reduced cost, by choosing for the casingparts a particular combination of materials. Accordingly, we constructthe top housing member of a material having a high degree of dimensionalstability, without regard for its arc resistance characteristics; and weconstruct the bottom housing member of 12 a material having a highdegree of arc resistance characteristics, without regard for itsdimensional stability characteristics.

We define a material having a high degree of dimensional stability asbeing one which is such thatstructure of the type described hereinmolded therefrom do not display any change in dimensions in ordinarystorage or use such as might prevent proper fitting of parts mountedtherein or thereon or cause malfunctioning of the apparatu-s. Suchdimensional changes for instance maybe caused by shrinkage, swelling,warping, or cold-flowing. The term cold-flowing is used to meanpermanent distortion or yielding of a material under sustained pressureat ordinary temperatures, i.e., (0-100 C.).

We define a material having a high degree of are resistance as being onewhich has an arc resistance rating as testedby the American Society'forTesting Materials test method No. D495, of at least seconds. I

We prefer to construct the top housing member of a general-purpose type,wood-flour filled phenohformaldehyde molding compound. We prefer toconstruct the bottom housing member of an alpha-cellulose filledurea-formaldehyde molding compound.

General-purpose wood-flour filled phenolic molding compound, as is wellknown, has a high degree of dimensional stability. Its arc resistance,however, is relatively poor, since it tracks or forms a conductive pathwhen exposed to arcing.

Urea-formaldehyde molding compound, with alphacellulose filler, does nothave a high degree dimensional stability in configurations such asrepresented by housing member 11. its arc resistance, however, is of ahigh degree, being in the neighborhood of to seconds by the A.S.T.M.test method referred to.

By using each of these materials in an application where its superiorcharacteristic is important and its other characteristics relativelyunimportant,, we are able to provide a circuit breaker of substantiallyreduced cost.

Instead of general-purpose phenolic molding com pound, we may of courseuse for the top housing member any one of a number of other plasticmolding materials having a high degree of dimensional stability;Specifically, we may use melamine-formaldehyde molding compounds, orpolyester type molding compounds. Various other materials having a highdegree of dimensional stability will occur to those skilled in the art.

In addition, while we prefer to use a urea-formaldehyde molding compoundfor the bottom housing member for cost reasons, we may utilize any ofthe well known suitable molding materials having a high degree of arcresistance, i.e., a material having an arc resistance of 80 seconds ormore. Such materials include the melamine and polyester materials aswell as glass-bonded mica or Mycalex materials and phenolics, epoxyresins and other materials incorporating special fillers to increasetheir are resistance.

The tapering construction of the slots 123 and 124 provides for easy andrapid insertion of the assembled mechanism is place in the top housingmember 10 and also provides accurate final positioning. By means of theassembly shown the operating mechanism including its supporting framemembers is mounted in the insulating casing without being positivelyfastened thereto. This construction not only saves time and expense inassembly, but provides a safer construction than those utilizing screwsgoing through the housing which need to be insulated from outside thehousing.

The manual operating member 74 is generally U-shaped and thesidesthereof extend alongside of the mounting side frames 57 and 58 of theoperating mechanism. Space or clearance must therefore be providedbetween the inner Walls of the mounting chamber 16 and the sides of theframe members 57 and 58 to allow free movement of the manual operatingmember 74. This spacing is also provided by the extended projections 61and 62.

The common trip bar 87 is preferably made in the form of a relativelywide, thin, flat member so that it is adapted to act as a shieldinterposed between the entrance portions 33 of the arc extinguishingchambers and the trip device including the bimetallic strip 50, themagnetic core 118 etc.

The design of the circuit breaker housing and especially the lowerhousing member 11 is such as to provide substantially no venting fromthe arc extinguishing chamber outside of the casing. This totalenclosure affords maximum safety to surrounding apparatus. While much ofthe hot gases generated by arc interruption are forced out of theentrance 33 against the flexible conductor 53 and toward the tripdevice, serious damage is prevented to these parts. Damage to theflexible conductor 53 is prevented although it is directly in the streamof are extinguishing gases by reason of the flexible woven glass sheath54. It has been found that although the temperature of the flame andgases is suflicient to melt such glass and produce a sizable hole insuch a sheath, that even thereafter the effect of such flame and gaseson the conductor 53 is not further destructive. This is assumed to bebecause the melted glass coats the individual strands of the flexibleconductor affording it protection.

While we have shown only two embodiments of our invention, it will bereadily appreciated that many modifications thereof may easily be made,and We intend therefore, by the appended claims, to cover all suchmodifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A multipole electric circuit breaker comprising a generallyrectangular insulating casing having a plurality of pole chambers, aplurality of arc extinguishing chambers in side-by-side relation in onecorner thereof, a stationary contact supported within said housing ineach of said are extinguishing chambers, a movable contact arm pivotallysupported within said housing above each of said are extinguishingchambers and carrying a movable contact thereon adapted to move betweenopen and closed circuit positions out of and into contact with thestationary contact therein, operating mechanism above said areexinguishing chambers and adapted to move all of said movable contactsbetween said open and closed circuit positions, a current responsivetrip device within each of said pole chambers and including at least aportion extending adjacent each of said are extinguishing chambers, acommon trip bar having a portion extending transversely across all ofsaid pole chambers between said current responsive trip means and saidare extinguishing chamber comprising a relatively wide thin flat memberserving to shield said current responsive trip means from areinterruption products generated by interruption of short circuitcurrents within said are extinguishing chamber.

2. A multipole electric circuit breaker comprising a generallyrectangular insulating housing including a plurality of side-by-sidepole chambers, each having an arc extinguishing chamber at one endthereof, a relatively stationary contact in each of said chambers, amovable contact arm of relatively Wide thin flat material supported forpivotal movement about an axis above each said are extinguishing chamberand carrying a relatively movable contact movable thereby within saidarc extinguishing chamber into and out of engagement with saidrelatively stationary contact, current responsive trip means in saidinsulating casing adjacent each of said are extinguishing chambers, acommon trip bar having a portion extending transversely across all ofsaid pole chambers between said current responsive trip means and saidare extinguishing chambers comprising a relatively wide thin flat memberserving to shield said current responsive means from are interruptionproducts generated in said are extinguishing chamber, and a transverselyextending contact cross arm of relatively wide thin flat material operatively connected to said operating mechanism and extending across saidpole chambers above said are extinguishing chambers, said contact armsand said contact cross arm cooperating to shield said operatingmechanism from the effects of arcs generated in said are extinguishingchamber.

3. A multipole electric circuit breaker comprising a top insulatinghousing member having three longitudinally extending recesses thereinand a first transversely extending recess contiguous with saidlongitudinally extending recesses, a contact cross arm supported in saidtransversely extending recess, a movable contact arm in each of saidlongitudinally extending recesses carried by said contact cross arm, asingle operating mechanism supported in one of said longitudinallyextending recesses and including a trip member biased for movement tocause automatic opening movement of all of said movable contact arms,and a latch member normally restraining said trip member, a bottominsulating housing member having three longitudinally extending recessestherein, a stationary contact in each of said longitudinally extendingrecesses, a second transversely extending recess in said bottom housingmember contiguous with each of said longitudinally extending bottomrecesses, a common trip bar carried by said latch member in said onelongitudinally extending top recess and extending in said transverselyextending bottom recess across all said pole chambers.

4. An electric circuit breaker comprising a top insulating housingmember having a recess therein, a bottom insulating housing member, astationary contact mounted in said bottom housing member, a movablecontact carried by said top housing member and operable to engage anddisengage said stationary contact when said top and bottom housingmembers are fastened together, a preassembled operating mechanism insaid recess adapted to operate said movable contact and including aplurality of movable parts pivotally supported between two opposedmechanism side frames, means positioning said operating mechanism insaid recess without said mechanism being positively fastened to said tophousing member, means carried by said bottom housing member for engagingsaid mechanism side frames when said top and bottom housing members arefastened together to retain said mechanism in said top housing member,and fastening means connecting said top and bottom housing memberstogether.

5. An electric circuit breaker comprising an insulating casing, a pairof relatively movable contacts within said casing, operating mechanismfor operating said relatively movable contacts between open and closedcircuit conditions, said operating mechanism comprising a pair ofopposed side frame portions and an operating member having portionsextending along the outer side of said opposed side frame portions, arecess in said insulating casing, means for supporting said operatingmechanism within said recess Without said mechanism being positivelyfastened to said casing includng a plurality of projections carried bysaid opposed side frame portions and directed outwardly thereof andadapted to engage the side walls of said insulating casing recesswhereby to support said mechanism in said recess with said side frameportions spaced from said side Walls to provide clearance for movementof said operating member between said side walls and said side frames.

6. An electric circuit breaker comprising a two-part insulating housingincluding a top part and a bottom part, a recess in said top partadapted to receive and contain an operating mechanism, a recess in saidbottom part, a relatively stationary contact in said bottom recess, arcextinguishing means in said bottom recess, operating mechanism includinga pair of opposed side frame portions, a plurality of spacer pinssupporting and spacing said side frame portions fiom each other, amanually 15 operable member having side portions overlying the outerportions of said side frame portions, said operating mechanism beingadapted to be received within said recess in said top part of saidinsulating enclosure, said spacer pins having integral extensionsextending through said side frame portions and projecting therebeyondand adapted to engage the side walls of said recess to support saidoperating mechanism in said recess with said side frame portions spacedfrom the side wall portions of said recess to provide clearance for saidoperating handle.

7. An electric circuit breaker comprising an insulating casing, a pairof relatively movable contacts within said casing, operating mechanismfor operating said contacts between open and closed circuit positions,said operating mechanism being adapted to be preassembled beforeinsertion in said casing, said casing having a recess adapted to receiveand contain said preassembled operating mechanism, said operatingmechanism including a plurality of relatively short projectionsprojecting outwardly from the outer sides thereof, said recess including a plurality of slots in the side walls thereof corresponding to saidprojections and adapted to receive said projections when said mechanismis inserted in said recess to accurately position said mechanism withinsaid casing without said mechanism being positively fastened thereto.

8. An electric circuit breaker as set forth in claim 7 wherein saidslots in said recess include an intermediate portion of narrower widththan the extreme inner portion whereby to provide a snap-in retainingmeans for holding said mechanism in said casing.

9. An electric circuit breaker comprising a bottom insulating housingmember having an arc extinguishing chamber therein, a top insulatinghousing member having a recess therein, a stationary contact mounted insaid are extinguishing chamber, a movable contact, an operatingmechanism adapted to move said movable contact into and out ofengagement with said stationary contact in said are extinguishingchamber, said operating mechanism being received within said recess insaid top member without being positively fastened thereto, said areextinguishing chamber having a ledge portion along at least oppositesides thereof, an arc extinguishing cham ber cover of insulatingmaterial supported on said ledge portions, fastening means connectingsaid top and bottom members together in superposed relation, saidmechanism including a portion adapted to be engaged by said cover toretain said mechanism in said recess in said top member.

10. An electric circuit breaker comprising an insulating housing memberhaving a recess therein, a relatively stationary terminal member mountedin said recess, a bimetallic strip in said recess extending generallyparallel to said terminal member and having one end connected thereto, amovable contact member, means connecting the other end of saidbimetallic strip to said movable contact member, operating mechanism foroperating said movable contact including a normally latched memberreleasable to effect automatic opening movement of said movable contact,a magnetic armature plate between said bimetallic strip and saidterminal member, molded bearing surfaces in said recess adapted topivotally support said armature, said armature including an extensionextending around said bimetallic strip, and biasing means biasing saidarmature into engagement with said bimetallic strip and also intoengagement with said molded pivot bearings, said armature also includinga portion adapted to engage said releasable trip member to causeautomatic opening of said circuit breaker.

11. An electric circuit breaker comprising at least two relativelymovable contacts movable between open and closed circuit positions,operating mechanism for operating said contacts between said open andclosed circuit positions, said operating mechanism including a membermovable to cause automatic opening of said contacts, a trip deviceincluding a relatively stationary terminal memher, an elongatedbimetallic strip having one end con nected to said terminal member andhaving its intermediate portion extending parallel to butspaced apartfrom the intermediate portion of said terminal member, means connectingthe other end of said bimetallic strip toone of said relatively movablecontacts whereby said bimetallic strip is adapted to carry currenttherethrough, a magnetic armature member pivotally supported in theinsulating material of said casing at one end and having a lost motionconnection with said bimetallic strip at the other end, a magnetic coremember carried by said bimetallic strip on the opposite side thereoffrom said armature member, said armature member being attracted towardsaid bimetallic strip by said' magnetic core member upon the occurrenceof relatively high overload currents, and biasing means biasing saidarmature-away from said bimetallic member, said movement being limitedby said lost-motion connection, said biasing member also biasing saidarmature member into said molded bearings.

12. An electric circuit breaker comprising a two part insulating casingincluding a top part and a bottom part, said bottom part including arelatively stationary contact and are extinguishing means adjacentthereto, said top part including operating mechanism for operating saidcontact between open and closed circuit position, said operating memberincluding a member releasable to cause automatic opening of saidcontacts, said top part also including a trip device for causingreleasing movement of said releasable trip member upon the occurrence ofpredetermined electrical conditions, said trip device including aterminal member mounted against one wall of said casing and an elongatedbimetallic strip having one end attached to said terminal member andhaving its intermediate portion extending parallel to but spaced apartfrom the intermediate portion of said terminal member, and a magneticarmature extending generally parallel to said bimetallic strip andpivotally supported at its upper end in generally V-shaped moldedbearings in saidinsulating casing said armature having a limited lostmotion connection with the outer end of said bimetallic. strip,.

a magnetic core member carried by said bimetallicv strip:

on the side thereof opposite said armature member, said armature memberbeing attracted toward said bimetallic.

strip by said magnetic core member upon the occurrence bimetallic memberand also in retained engagement in:

said molded bearings.

References Cited in the file ofthis patent UNITED STATES PATENTS2,020,332 Sachs Nov. 12, 1935 2,073,965 Jackson Mar. 16, 1 937 2,094,966Sachs Oct. 5, 1937 2,214,695 Jennings Sept. 10, 1940 2,348,228 Scott 1May 9, 1944: 2,390,039 Slayter et a1. Nov. 7, 1945 2,416,163 Dyer et allFeb. 18, 1947. 2,419,125 Dorfman et a1. Apr. 15, 1947' 2,446,027 ScottJuly 27, 1948 2,558,908 Paige July 3', 1951 2,645,693 Cole et all July14, 1953 2,678,359 Brumfield' May 11, 1954' 2,797,277 Dorfman et a1 -1June 25, 1957 2,797,278 Gelzheiser et al June 25, 1957 2,806,109Sterling Sept, 10, 1957 2,811,607 Dorfman et al Oct. 29, 1957

